1. Field of the Invention
The present invention relates, in general, to use of nanotechnology, and, more particularly, methods to produce significantly improved material performance through the use of composite nanoparticles.
2. Relevant Background
Powders are used in numerous applications. They are the building blocks of electronic, telecommunication, electrical, magnetic, structural, optical, biomedical, chemical, thermal, and consumer goods. On-going market demands for smaller, faster, superior and more portable products have demanded miniaturization of numerous devices. This, in turn, demands miniaturization of the building blocks, i.e. the powders. Sub-micron and nano-engineered (or nanoscale, nanosize, ultrafine) powders, with a size 10 to 100 times smaller than conventional micron size powders, enable quality improvement and differentiation of product characteristics at scales currently unachievable by commercially available micron-sized powders.
Nanopowders in particular and sub-micron powders in general are a novel family of materials whose distinguishing feature is that their domain size is so small that size confinement effects become a significant determinant of the materials' performance. Such confinement effects can, therefore, lead to a wide range of commercially important properties. Nanopowders, therefore, are an extraordinary opportunity for design, development and commercialization of a wide range of devices and products for various applications. Furthermore, since they represent a whole new family of material precursors where conventional coarse-grain physiochemical mechanisms are not applicable, these materials offer unique combination of properties that can enable novel and multifunctional components of unmatched performance. Yadav et al. in a co-pending and commonly assigned U.S. patent application Ser. No. 09/638,977 which along with the references contained therein are hereby incorporated by reference in full, teach some applications of sub-micron and nanoscale powders.
It has been anticipated by those skilled in the art that size confinement could potentially produce materials with significantly improved strength, toughness, hardness, and other mechanical properties. However, size confinement has been difficult to reduce to commercial practice. The reasons for this failure, in part, include (a) current inability to retain the nanoscale grain size when nanoparticles are post-processed into a final commercial product, and (b) agglomeration and aggregation of nanoparticles that in turn produces defects and poor bonding at interfaces.
Yet another method of improving the mechanical performance of materials that is known to those in the art is to employ particles to dispersion strengthen materials. Dispersion strengthening is a method used to increase the strength and high temperature performance of metal alloys by incorporating a fine distribution of hard particulates within a load-bearing matrix. These materials are formed, for example, by mixing particles with a matrix material comprising the metal, metal alloy, or other material to be strengthened. This method takes advantage of the fact that dislocation motion is hindered by the presence of the fine particulate. It is expected that as nanoparticles replace microparticles in dispersion-strengthened materials, the performance of these materials will increase.
However, it has been difficult to use nanoscale particulates in commercial dispersion strengthening applications because of poor bonding at the matrix and the nanoparticle dispersant interface. The lack of an intimate, uniform bonding between the matrix and dispersant materials results in sub-optimal performance of the composite materials. Further, conventional techniques experience difficulty in achieving and maintaining a homogeneous distribution of the nanoparticles in the matrix.
In general, the commercial promise and social benefits of nanotechnology are currently limited by the difficulty in post-processing nanoparticles into nanotechnology products. There is a need for a technology that can address these post-processing limitations.